Color cathode-ray tube with temperature equilization for plurality of electron gun filaments

ABSTRACT

An electron gun assembly for color cathode-ray tube comprising three electron guns which are arranged approximately parallel in the same plane and each of which includes a heater, a cathode and a plurality of electrodes, and at least one connection member to which the heaters are connected at substantially equal intervals, wherein the area of the connection member portion to which the heater belonging to the central electron gun is connected is made larger than that of each of the areas of the connection member portions to which the other heaters are connected, so that the temperatures of the cathodes of the three electron guns are made substantially the same during activation step and operation thereof.

[ Mar. 25, 1975 United States Patent n91 Yamauchi COLOR CATHODE-RAY TUBE WITH Primary Examiner-Robert Sega] TEMPERATURE EQUILIZATION FOR Attorney, Agent 0r Firm-Craig & Antonelli [57] ABSTRACT An electron gun assembly for color cathodecomprising three electron guns which are arran proximately parallel in the same N U G N 0 R T C E L E F 0 S WT N LE AM WA Lu PF ray tube [75] Inventor: Masaaki Yamauchi, Mobara, Japan ged applane and each of e and a plurality of {73] Assignee:

Filed:

which includes a heater, a cathod nection member to which the heaters are connected at subst electrodes, and at least one con [21] Appl. No: 451,285 nntially cqunl ction member ging to the central ectron gun is connected is made la each of the areas of the connection intervals, wherein the area of the conne portion to which the heater belon el rger than that of member portions [30] Foreign Application Priority Data Sept. 21, 1973 48-106035 enn mmw t t a a ma C O a e mm l r h ed 6 m m of c w 6 mmh ad 0V5 S f a m tal aC e hemt h5 fi w hfwi m a F 83 6 br n. um med .w n h DIS Wmnp Oe w tt S 74 7 M94 32 1. 1 31] 9,044, n 0 4 35 l i 99 MF N M WH3 m m Hr Na U8 U L COM s m U .F N 555 llil 1 Claim, 3 Drawing Figures PATENTED lR25 ii- I COLOR CATHODE-RAY TUBE WITH TEMPERATURE EQUILIZATION FOR PLURALITY OF ELECTRON GUN FILAMENTS The present invention relates to an electron gun assembly for color cathode-ray tube or more in particular to an in-line type of the electron gun assembly comprising three electron guns arranged approximately parallel in substantially the same plane.

Generally, electron gun assemblies for color cathoderay tube are classified into bipotential and unipotential types depending on the manner in which electrodes are arranged. Further, they are grouped into delta and inline types depending on the arrangement of the electron guns. The conventional in-line type of electron gun assembly in which three electron guns each with a heater, a cathode and a plurality of electrodes are arranged approximately parallel in substantially the same plane has the disadvantage that the cathode belonging to the central electron gun is heated more than the cathodes belonging to the other electron guns since it receives radiation heat from the cathodes and heaters of the other electron guns. This fact adversely affects the activity of the cathodes in the manufacturing processes of the color cathode-ray tube, especially during the activation step thereof and also shortens the service life of the central cathode.

In one of the efforts to overcome such a problem, the cathode associated with the central electron gun is made larger than the cathodes associated with the other electron guns thereby to increase the thermal radiation and thermal conductivity of such a central cathode. According to such a method, however, the cathode for the central electron gun is likely to be mistaken for the cathode for one of the other electron guns on an assembly line for mass production.

Accordingly, it is an object of the present invention to provide an in-line type of electron gun assembly for a color cathode-ray tube comprising similar cathodes for the three electron guns which can be maintained at substantially the same temperature.

According to the present invention, there is provided an electron gun assembly for a color cathode-ray tube comprising three electron guns which are arranged approximately parallel in the same plane and each of which includes a heater, a cathode and a plurality of electrodes, and at least one connection member to which the respective heaters are connected at substantially equal intervals, wherein the area of the connection member portion to which the heater belonging to the central one of the electron gun is connected is made larger than that of each of the areas of the connection member portions to which the heaters belonging to the other electron guns are connected.

The above and other objects and features of the present invention will become apparent when reading the following detailed description of the prior art and the present invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram schematically showing an example of a conventional electron gun assembly for color cathode-ray tube;

FIG. 2 is a diagram schematically showing the construction of a heater connection member of the electron gun assembly of FIG. 1; and

FIG. 3 is a diagram schematically showing the construction of a heater connection member of an electron gun assembly'for color cathode-ray tube according to the present invention.

Referring to FIG. 1 showing an example ofa conventional in-line type of electron gun assembly for color cathode-ray tube, electron guns 2 and 4 among the electron guns 2, 3 and 4 for red, green and blue respectively supported on support members 1 of bead glass have their axes inclined by about l in such a manner as to intersect with each other at a point on a color selective electrode not shown. As shown in FIG. 2, connection members 8 and 9 connected to heaters 5, 6 and 7 associated respectively with the electron guns 2, 3 and 4 are fixedly supported by the support members 1 through legs 81, 82 and 83 extending from the connection members 8 and 9. Cathodes 10, 11 and 12 into which the heaters 5, 6 and 7 are inserted are contained respectively in the first grid electrodes 13 which constitute the electron guns.

In the above-described construction, when the heaters 5, 6 and 7 are heated upon application of a voltage to the connection members 8 and 9, the cathodes 10, l l and 12 are heated so that electron beams are emitted from the respective electrodes to form a desired image on a screen.

However, the conventional electron gun assembly of the above-mentioned construction has the disadvantage that the radiation heat received by the central cathode 11 from the heaters 5 and 7 are the other cathodes 10 and 12 causes the cathode 11 to be increased in temperature more than the other cathodes l0 and 12. This phenomenon has a great adverse effect on the initial characteristics of the cathodes in the manufacturing processes of cathode-ray tubes, especially on the activation step thereof, and also shortens the service life of the cathode 11 compared with those of the other cathodes 10 and 12.

According to the present invention, such a disadvantage is obviated by enlarging the area of the portion of the heater connection member to which the heater associated with the central cathode is connected, with the result that the heat radiation efficiency of that particular portion of the connection member is increased thereby to maintain all the cathodes at substantially the same temperature.

Referring to FIG. 3 showing schematically the construction of an electron gun assembly for a color cathode-ray tube according to the present invention, especially the connection members thereof, the reference numerals same as those inserted in FIG. 2 show the same elements. In FIG. 3, reference numerals and show connection members as the feature of the invention, to which leads 51, 61 and 71 of the heaters 5, 6 and 7 are secured at substantially equal intervals by means of spot welding or the like. And the central portions 80a and 90a of the connection members 80 and 90 to which the heater 6 is connected are made larger.

In this arrangement, when the heaters 5, 6 and 7 are heated upon application of power thereto through the connection members 80 and 90 thereby to heat the cathodes 10, 11 and 12, the cathode 11 positioned at the center tends to be increased in temperature more than the other cathodes 10 and 12 due to the aforementioned reason. However, in view of the fact that the central portions 800 and 90a of the connection members connecting the heaters have a larger area than the other portions thereof and hence radiate more heat, the temperature of the heater 6 secured to the particular portions is maintained as low as the other heaters due to the higher radiation efficiency thereof coupled with small thermal conduction of the leads 61. As a result, the cathode 11 is maintained at the temperature same as the other cathodes l and 12.

In this case, it will be needless to say that the areas of the central portions 80a and 90a of the connection members 80 and 90 are required to be selected such that the rise in temperature of the cathode 11 is maintained the same as those of the cathodes l0 and 12.

Though the embodiment shown in FIG. 3 employs two connection members, the present invention may be applied with equal effect, employing a single connection member comprising an insulator secured to at least one support member and separate conductors connected respectively to the leads of the heaters of the respective electron guns, the area of the central conductor being made larger than each of those of the other conductors. In this case, each conductor is divided such that the portions of the conductor to which a couple of loads of the heater are connected are electrically insulated from each other.

Further, though the present invention has been described in the case where three heaters are connected in parallel, the invention may be applied with equal effect, employing three heaters connected in series. Also, in place of three electron guns separated completely for the respective colors, an integrally formed electron gun may be employed in the invention.

In summary, in the electron gun assembly for a color cathode-ray tube according to the present invention,

the area of that portion of the connection member to which the central heater is connected is'made larger for an increase in heat radiation therefrom, so that the temperature of the central heater does not rise to an undesirably high level, thus maintaining all the cathodes at the same temperature. As a result, the activity of the cathodes is not adversely affected and the shortened life of the central cathode as compared with those of the other cathodes is successfully prevented. resulting in a longer useful life of the electron gun assembly as a whole.

What is claimed is:

1. An electron gun assembly for a color cathodc-ray tube comprising three electron guns which are arranged approximately parallel in the same plane and each ofwhich includes a heater, a cathode and a plurality of electrodes, at least one connection member to which the respective heaters are connected at substantially equal intervals, wherein the area of the connection member portion to which the heater belonging to the central one of the electron gun is connected is made larger than that of each of the areas of the connection member portions to which the heaters belonging to the other electron guns are connected, the area of the connection member portion to which the heater belonging to the central electron gun is connected being selected so as to maintain the rise in temperature of the cathode belonging to the central electron gun substantially the same as those of the cathodes belonging to the other electron guns.

l l l 

1. An electron gun assembly for a color cathode-ray tube comprising three electron guns which are arranged approximately parallel in the same plane and each of which includes a heater, a cathode and a plurality of electrodes, at least one connection member to which the respective heaters are connected at substantially equal intervals, wherein the area of the connection member portion to which the heater belonging to the central one of the electron gun is connected is made larger than that of each of the areas of the connection member portions to which the heaters belonging to the other electron guns are connected, the area of the connection member portion to which the heater belonging to the central electron gun is connected being selected so as to maintain the rise in temperature of the cathode belonging to the central electron gun substantially the same as those of the cathodes belonging to the other electron guns. 